AT&T may be quietly enabling FaceTime over cellular for customers on unlimited data plans, according to a report in MacRumors. AT&T originally limited cellular FaceTime to customers on the carrier's new shared data plans. After a public outcry, AT&T later expanded FaceTime to customers who are connected to the carrier's 4G LTE network and have either a tiered or shared plan.
MacRumors forum user kre62 noticed that his iPhone 4S and iPhone 5 now support FaceTime over cellular even though he is on an unlimited plan. Several other users in the MacRumors thread confirmed this report, and BGR also claims its two iPhone 5 handsets have FaceTime enabled on unlimited data plans.
AT&T has not announced that it is activating cellular FaceTime service for unlimited data plans, so it is possible that this is just a glitch. We have reached out to AT&T to confirm these reports and will update the post when we receive a response. [Editor's note: When we tried activating FaceTime on an iPhone 5 with an unlimited data plan it popped up the familiar warning to call AT&T and purchase a plan that supported the feature so at this time we cannot confirm this is happening on any large scale.]
To check if FaceTime over cellular is now available on your iPhone, you should first reboot your iPhone for the service to go into effect. Then open Settings > General > Cellular and scroll down to see if the FaceTime toggle is on. If it is on, then you should be able to initiate a FaceTime call over AT&T's cellular connection.